I don't know if this will generate many examples that don't fall under subtropes, but seems like a case of Missing Supertrope Syndrome. Simply put, two characters who aren't in a romantic relationship pretend to be. Naturally, there's a high likelihood of them Becoming the Mask, or at least one character claiming It Meant Something to Me. Supertrope of Undercover as Lovers, Operation: Jealousy, The Beard, Citizenship Marriage, Shock Value Relationship, Boyfriend Bluff. Contrast Secret Relationship. See also Fake Out Makeout.
Examples:Anime and Manga
- The premise of Nisekoi, translated as "False Love". The lead characters are pressured into pretending to be in a romantic relationship to keep their Feuding Families from getting out of hand.
- Two KAOS agents once pretended to be in love, sharing a public kiss to escape detection by CONTROL. Max and 99 likewise often masqueraded as a married couple on missions before they got hitched for real.
- Booth and Brennan did this several times on Bones before getting together for real. They went undercover as "Buck and Wanda" a couple of times, and once they did it at Brennan's school reunion.
- The premise of the britcom Spaced is that the main characters believe they have a Single-Issue Landlord who will only rent the flat to a couple. It eventually turns out this was all based on a misprinted advertisement.
- Frasier pretends to be Roz's date at a family reunion when she's recently been dumped and can't face her competitive, passive-aggressive sisters.
- Martin pretends to date the mother of Frasier's Sitcom Arch-Nemesis as a prank on the pair of them.
- In Victor/Victoria, when Victoria starts masquerading as the female impersonator Victor she and Toddy pretend to be lovers.
- Fry on Futurama gets himself into a fake relationship triangle. First he pretends to be Amy's boyfriend so that her parents would stop trying to set her up with men. Later he pretends to be Leela's boyfriend so that Zapp Brannigan will stop hitting on her. This becomes awkward when all of them are having dinner at the captain's table in front of both Amy's parents and Zapp.
Hello, Unknown Troper. You'll need to get known to lend a hand here.